Center coupled filter



Oct. 1, 1957 L'. M. lBsEN ETAL 2,808,572

CENTER COUPLED FILTEQ;

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CENTER COUPLED FILTER Lloyd M. Ibsen, North Hollywood, and William E. Whittington, Burbank, Calif., assignors to Collins Radio Company, Cedar Rapids, Iowa, a corporation of iowa Application November 17, 1954, Serial No. 469,388

Claims. (Cl. S33- 71) This invention relates in general to electromechanical filters and in part to a center-coupled filter which elimiiates spurious responses and which is relatively broad and.

As developments have been made in electromechanical filters, more and more modifications and refinements have been made. The basic theory of mechanical filters wherein electrical energy is transformed to mechanical energy, filtered and then changed back to electrical energy is not new. For example, see the patent to H. A. Burgess entitled Mechanical Wave Filter, Patent No. 1,666,681, issued April 17, 1928, `and the patent to H. C. Harrison entitled Device for the Transmission of Mechanical Vibratory Energy, Patent No. 1,678,116, issued July 24, 1928. The patent to M. L. Doelz entitled Filter Using Transverse Supporting Means, Patent No. 2,656,516, issued October 20, 1953, describes a practical filter which has been constructed and successfully operated by the owner of the present invention. The present invention relates to an improved electromechanical filter which comprises a plurality of resonating discs coupled together by a central drive and output wire. A plurality of supporting wires are attached to the peripheries of the discs and furnish mechanical support.

A feature of the present invention is an electromechanical filter which has very broad band and wherein the spurious response is greatly reduced.

Further objects, features and advantages of this invention will become apparent from the following description and -claims when read in View of the drawings, in which:

Figure 1 is a top view of the electromechanical filter;

Figure 2 is a sectional view taken on line 2-2 of Figure 1; and

Figure 3 is a side view illustrating a modification of the invention.

Figure 1 illustrates a base plate 10 on which is mounted a pair of supporting stand-offs 11 and 12. Standoffs 11 and 12 are each formed in two parts with bottom parts 13 and 14, respectively, and top parts 15 and 16, respectively.

Set screws 17 and 18 pass through the stand-offs and attach the upper and lower parts together and also attach the stand-offs to the base plate 10. A pair of cylindrical members 19 and 21 are held between the upper and lower parts of the stand-offs. A pair of coil forms 22 and 23 are supported within the cylindrical members 19 and 21, and support windings 24 and 2.6, respectively. Winding 24 has leads 27 and 28 which are connected to terminals 29 and 31 mounted on the base plate 10. The winding 26 has leads 32 and 33 which are connected respectively to terminals 34 and 36 that are attached to the base plate 10. Attached to one end of the cylindrical member 19 is a disc 37. The disc 3'7 is formed with a central opening 38 for a purpose to be later described. One end of the cylindrical member 21 has attached thereto a disc 39 which 7is formed with a central opening 41.

nited States Patent O rice A plurality of supporting wires 42 extend from disc 37 to disc 39 and are welded to the peripheries thereof. Mounted between the discs 37 and 39 are a plurality of active resonating discs 43 through 48. The coil forms 22 and 23 are formed with openings 49 and 51, respectively, and a longitudinal driving wire 52 extends through the openings 49 and 51, and pass through the discs 37, 39 and 43 through 48. The drive wire 52 does not engage the discs 37 and 39 because the openings 38 and 41 are larger than the outer diameter of the wire. However, drive wire 52 is connected to each of the discs 43 through 48 at the center. This connection is made by drilling holes through the discs 43 through 48 and by welding the wire 52 to each disc.

The above described structure results in an electromechanical filter which has relatively broad band and in which spurious responses are substantially eliminated. A biasing magnet 53 is mounted adjacent coil 24 and a magnet 54 is mounted adjacent coil 26. For example, the driving rod might be from 15 to 30 thousandths in diameter and might be constructed of a nickel-iron alloy as NiSpan C. The discs might also be constructed of NiSpan C. Applicant has constructed filters according to this invention which has a passband of 455 kilocycles,

Figure 3 illustrates a modification of this invention wherein the number of supporting Wires have been increased until they form a solid cylinder 50. This structure forms a substantially enclosed mechanical resonator. The cylinder Si) is attached to the edges of the discs.

Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited yas changes and modifications may be made therein which are within the full intended scope of the invention, as defined by the appended claims.

We claim:

1. An electromechanical filter comprising a base member, a pair of supporting means attached to said 4base member, a first `supporting disc `attached to one of said supporting means, a second supporting disc attached to the second supporting means, a plurality of supporting wires attached to the peripheries of said first and second supporting discs and extending between them, a plurality of active discs mounted between the first and second supporting discs and with their peripheries attached to the supporting wires, a drive wire extending through the supporting and active discs, said drive wire firmly attached to said active discs and said drive wire extending through openings formed in said supporting discs and out of engagement therewith.

2. An electromechanical filter comprising a base member, a pair of supporting means attached to said base member, a first supporting disc attached to one of said supporting means, a second supporting disc attached to the second supporting means, a plurality of supporting Wires attached to the peripheries of said first and second supporting discs and extending between them, a plurality of active discs mounted between the first and second supporting discs and with their peripheries attached to the supporting wires, a drive wire extending through the supporting and active discs, said drive wire firmly attached to sai-d active discs, said drive wire extending through openings formed in said supporting discs and out of engagement therewith, a driving winding mounted in the first supporting means, an output winding mounted in the second supporting means, and said drive wire extending thro-ugh the driving and output windings.

3. An electromechanical filter comprising a base member, a pair of supporting means attached to said base member, a pair of biasing magnets attached to said pair of supporting means, a first supporting disc attached to one of said supportin7 means a second supporting disc attached to the second supporting means, a plurality of supporting wires attached to the peripheries of said first and second supporting discs and extending between them, a plurality of active discs mounted between the first land second supporting discs and with their peripheries attaehed to the supporting wires, a drive wire `of magnetostrictive material extending through the supporting and active discs, said drive wire firmly attached to said active discs and said drive wire extending through openings formed in said supporting discs and out of engagement therewith.

4. An electromechanical filter comprising a base member, a pair of supporting means attached to said base member, a first supporting disc attached to one 4of said `supporting means, a second supporting disc attached to the second supporting means, a hollow supporting cylinder attached to the peripheries of said first and second supporting discs and extending between them, a plurality of active discs mounted between the first and second supporting discs and with their peripheries attached to the supporting cylinder, a drive wire extending through the centers of the supporting and active discs, said drive wire firmly attached to said active discs and said drive wire extending through openings formed in said supporting discs and out of engagement therewith.

5. An electromechanical filter comprising a base member, a pair of standoffs attached to said base member, a rst supporting disc attached to one of said standoffs, a second supporting disc attached to the second standoff, supporting means attached to the peripheries of said first and `second supporting discs and extending between them, a plurality of active discs mounted between the first and second supporting discs and with their peripheries attached to the supporting means, a drive wire extending through the centers of the supporting and active discs, said drive wire rmly attached to said active discs, and said drive wire extending through openings formed in said supporting discs and out of engagement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,678,116 Harrison July 24, 1928 2,501,488 Adler Mar. 21, 1950 2,617,882 Roberts Nov. 11, 1952 2,693,580 Peterson Nov. 2, 1954 

